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nervous system and sensory - Coggle Diagram
nervous system and sensory
structure of nervous system
types of neuron
sensory
Conduct action potentials toward the CNS
Sensory neurons detect the internal and external environments
facilitate motor coordination
motors
conduct action potentials away from CNS towards muscles or glands
intemeuron
conduct action potentials within CNS from 1 neuron to another
primarily between sensory and motor neurons
cell membrane potential
A cell membrane’s surface is usually electrically charged (polarized) compared with its inner contents due to unequal amounts of positive and negative ions.
Adequate stimulation of a neuron causes generation of an electrical impulse in response
An action potential is a change in neuron membrane polarization and a return to its resting state
An action potential forms a nerve impulse propagated along an axon
neuron communication
synapses
Axodendritic synapses are those between the axon endings of a neuron and the dendrites of other neurons.
Axosomatic synapses are those between axon endings of one neuron and soma of others
neuromuscular junction - synapse between a neuron and a muscle cell
postsynaptic neuron - neuron receiving impulse
synaptic transmission - process of impulse crossing the synaptic cleft
presynaptic neuron - neuron carrying an impulse into a synapse
synaptic cleft - synapse junction gap between any 2 communicating neurons
Chemical synapses release and receive chemical neurotransmitters.
Information is transferred across chemical synapses beginning when an action potential arrives at an axon terminal.
Electrically coupled neurons allow for rapid transmission across electrical synapses (less common)
actions of neurotransmitters include effects on sleeping, anger, thinking, hunger, movement, memory, and many other functions.
Synaptic transmission is commonly affected by either the enhancing or inhibiting effects of neurotransmitters, their destruction, or the blocking of receptor binding
CNS
consists of the brain and spinal cord, located in the dorsal body cavity. It is the control center of the nervous system, integrating all its activitie
receives information from and sends information to the body.
key decision maker
PNS - messenger
consists of 12 cranial nerves and 31 spinal nerves
detects stimuli in and around the body and sends that information to the CNS. Communicates messages from the CNS to the body.
brain
cerebrum (largest part) - control higher brain function: inteprets sensory impulses, initates muscular movements, stores memories, handles reasoning and develops intelligence
basal nuclei - relays motor impulses from cerebral cortext . brain stem and spinal cord; assist in coordination of voluntary movements
diencephalon - thalamus; relays sensory impulses ascending from other areas of nervous system to cerebral cortex
hypothalamus: maintain homeostasis by regulating viceral activities (endocrine system)
brain stem
midbrain - reflex centers move eyes, head; maintain posture
pons - relays impulses between medulla oblongata and cerebrum; regulate breathing rate and depth
medulla oblongata - conducts ascending, descending impulses btwn brain and spinal cord; contains cardiac, vasomotor, respiratory control centers - various nonvital reflex control centres
cerebeilum - communicates w rest of CNS via tracts; integrates sensory info abt body part positions; coordinates muscle activities; maitains posture
spinal cord
thin column of nerves leading from the brain to the vertebral canal.
provides two ways of communication, to and from the brain, and contains the spinal reflex centers
brain protection
meninges - between bony covering and soft brain tissue membranes protects brain and spinal cord
cerebrospinal fluid - CSF surrounds the brain and spinal cord, maintaining a stable ionic concentration and protecting CNS structures. The brain floats in CSF, which cushions it and prevents the bottom of the brain from being crushed by its own weight. The CSF also helps to nourish the brain and may assist in carrying chemical signals concerning sleep and appetite.
blood brain barrier - acts to selectively allow certain molecules to pass and to keep others from reaching the brain. The maintenance of a constant environment keeps the brain’s neurons from firing uncontrollably.
peripheral nervous system
consists of the peripheral nerves connecting the CNS to other parts of the body
divided into sensory (afferent) and motor (efferent) divisions
process information between our bodies and our environments
structure
all neural structures that are outside the brain and spinal cord
somatic nervous system oversees conscious activities
autonomic nervous system oversees unconscious activities
sensory receptors
The sensory receptors of the PNS are specialized to respond to stimuli. They are sensitive to certain types of environmental changes.
Types of sensory receptors include-
Chemoreceptors-respond to chemicals in solution, including smelled or tasted molecules, changes in blood chemistry, and changes in interstitial fluid chemistry.
Mechanoreceptors- respond to mechanical forces such as pressure, touch, stretching, and vibrations.
Nociceptors- respond to stimuli that may be damaging, such as extreme heat or cold, excessive pressure, and inflammatory chemicals, resulting in pain.
Thermoreceptors- respond to temperature changes
general senses
The general senses of touch, pressure, temperature, and pain are spread throughout the body via muscle, joint, skin, and visceral receptors.
General sensory receptors are nerve endings of two types:
nonencapsulated (free) - mostly respond to temperature and painful stimuli in the skin and internal tissues, except for the brain.
encapsulated
reflex arc
A reflex is actually defined as a fast, automatic response to a specific stimulus. Reflex activity in the human body can be either inborn (innate) or learned (acquired).
Inborn reflexes are rapid and predictable motor responses to stimuli that are formed between neurons during human development.
They are involuntary and subconsciously maintain body posture, help to avoid pain, and control visceral activities. For example, a response to pain is triggered by an inborn spinal reflex that operates without assistance from the brain.
In a reflex arc, sensory impulses from receptors can reach their effectors without being processed by the brain. Some reflex arcs use interneurons. The five basic components of a reflex arc are a receptor, a sensory neuron, an integration center, a motor neuron, and an effector.
somatic and autonomic nervous system
sensory (afferent)
Impulses are carried toward the CNS from the body’s sensory receptors.
Somatic sensory fibers transmit impulses from the joints, skeletal muscles, and skin.
Visceral sensory fibers transmit impulses from the visceral organs of the ventral body cavity.
This sensory division informs the CNS of all events happening inside and outside the body.
motor (efferent)
Impulses are carried from the CNS to the effector organs, activating muscles to contract and glands to secrete.
They affect (cause) motor responses.
The two main parts of this motor division are the somatic nervous system and the autonomic nervous system (ANS).
somatic nervous system
Somatic motor fibers transmit impulses from the CNS to the skeletal muscles.
Includes 12 pairs of cranial nerves, which connect sensory organs.
The cranial nerves that only have sensory functions include the olfactory and optic nerves. Each of these has no parasympathetic fibers.
31 pairs of spinal nerves, which bring information into the spinal cord and carry messages from the cord to the effectors
voluntary nervous system
autonomic nervous system
Subdivides into the sympathetic and parasympathetic divisions.
ANS contains visceral motor nerve fibers regulating glandular, cardiac muscle, and smooth muscle activity
involuntary nervous system
autonomic nervous system (ANS)
divided into the sympathetic and parasympathetic divisions
Certain visceral organs have fibers from both divisions, controlling the activation or inhibition of their actions
sympathetic division prepares the body for stressful or emergency situations and is part of the fight-or-flight response
parasympathetic division functions in an opposite manner and is part of the rest-and-digest response
parasympathetic nerves - constrict pupils, slow heartbeat, constrict airways, contract bladder
sympathetic nerves - dilate pupils, inhibit salivation, increased heartbeat, relaexed airways
effects of ageing on nervous system
risk of stroke
fatty deposits accumulate in the blood vessels, there is a decrease in blood flow to the brain
increase the chances that an affected vessel will rupture, leading to symptoms of a stroke (cerebrovascular accident)
slower reaction time
brain processes nerve impulses more slowly, performance of certain tasks and reaction times often become slower
lderly person who exercises (both mentally and physically) often loses fewer nerve cells in the brain.
Consumption of two or more drinks of alcohol every day reduces brain function.
loss of neurons
Neuronal loss occurs. The amount and location of the loss varies substantially among different regions of the brain
Neuronal loss and shrinkage causes a decrease in brain weight and size
nervous system has large numbers of neurons, more than we probably ever use, so age-related neuron loss may not affect behavior appreciably until very old age
increase in neuroglia and deposits
Brain neurons accumulate abnormal intracellular deposits. Extracellular plaques may affect memory processing. When deposits and plaques exceed normal amounts caused by aging, clinical abnormalities may occur
characteristic of the brains of those with Alzheimer’s disease
changes in transmission efficiency
Decreased numbers of functional nerve cells may reduce the strength of the message being transmitted.
Fewer nerve cells result in more space to cross, and the coherence of the message may be disrupted, or random background noise (neural noise) could interfere with the clarity of the message
motor part of the older cerebral cortex may continue to respond for a time after stimulation ceases, and such aftereffects could blur or interfere with subsequent incoming messages
account for the increased time older people usually need to perform simple tasks as well as for their poorer retention and increased susceptibility to distraction in learning and memory tasks.
sensory
olfaction - sense of smell
masses of epithelium covering the upperpart of the nasal cavity, superior nasal conchae, and part of the nasal septum
have hair-like cilia, which help to differentiate among odors.
partially condensate from gases to fluids before receptors can detect them
analyzed by olfactory bulbs and interpreted in the olfactory complex of the brain
gustatory sense of taste
Taste pores have tiny projections called taste hairs, which are the sensitive parts of the taste receptor cells. Stimulation triggers an impulse on a nearby nerve fiber traveling to the brain.
The sense of taste is actually mostly based on the sense of smell to about 80%. Food lacks taste when the nasal passages are congested. This is why food doesn't taste good when you're having a flu.
Without smell, the sense of taste would be very inefficient and much of what we enjoy from various flavors could no longer be appreciated.
The five primary taste sensations are sweetness, sourness, saltiness, bitterness, and umami (deliciousness).
auditory - sense of hearing
detection of sound and the detection of body position, which enables us to maintain balance
external ear
Auricle (pinna): A funnel-shaped structure composed of elastic cartilage, thin skin, and small amounts of hair; most people refer to this structure as “the ear.” The auricle functions to funnel sound waves to the external acoustic meatus.
External acoustic meatus. Glands secrete cerumen, a yellow-brown waxy substance commonly referred to as earwax. Cerumen helps to trap foreign particles and repel insects from entering the ear
Eardrum (tympanic membrane): A semitransparent membrane covered by thin skin on the outside and mucous membrane on the inside that actually
moves back and forth in response to sound waves; it is the boundary between the outer and middle ear.
middle ear
tympanic cavity inside the petrous portion of the temporal bone is filled with air and contains the auditory ossicles
attached to the tympanic cavity wall by ligaments and bridge the eardrum and inner ear to transmit vibrations
Vibrations are passed to the auditory ossicles, which is held to an opening
Vibration of the stapes moves fluid within the inner ear > stimulate hearing receptors
inner ear
labyrinth structures are three semicircular canals, which aid in equilibrium, and a cochlea, which functions in hearing.
vestibule and expanded chamers with tiny macula containing many sensory hair cells function in equilibrium.
head is upright, the hairs project upward into a gelatinous material. When the head bends forward, backward, or to one side, the hairs bend to signal nerve fibers
a swelling called an ampulla houses sensory organs, each known as a crista ampullaris. Hair cells within a cupula are bent to signal the brain
visual - sense of sight
eyebrows consist of coarse, short hairs overlying the supraorbital skull margins and help to shade the eyes from light and to trap perspiration from the forehead.
eyelid has skin, muscle, connective tissue, and conjunctiva layers that collectively protect the anterior portion of the eye. The clinical term for eyelid is palpebrae.
conjunctiva is a thin, transparent mucous membrane associated with the eyelids and the exposed areas of the eye. The secretions of the conjuctiva help lubricate the surface of the eye.
Ganglion cell axons extend to the lateral geniculate ganglion of the thalamus, where they synapse
neurons form the optic radiations that project to the visual cortex.
Neurons from the nasal visual field (temporal retina) of one eye and the temporal visual field (nasal retina) of the opposite eye project to the same cerebral hemisphere
Axons from the nasal retina cross in the optic chiasm, and axons from the temporal retina remain uncrossed.
eyes
retina - contains the rods (black and white vision) and cones (sensitve to light than cones - provide vision in dim light without color
pupil - contracts, less light enters, controlling the amount of light the eye needs to see in specific conditions
iris - visible colored membrane of the eye, lying between the cornea and lens.
cornea - focus entering light rays and is continuous along its circumference with the white sclera